The present invention relates to a motor, in particular for the electrical drive of a clockwork, having a rotor which is mounted rotatably together with a shaft, the rotor being formed, in particular, of a permanent magnet with diametrically opposite permanent magnet poles, the motor having a coil arrangement with coils which are arranged at an angular distance apart of, in particular, 90.degree..
In one such known motor for the driving of a clockwork, a rotatably mounted rotor has diametrically opposite permanent magnet poles (Federal Republic of Germany OS 34 19 100). A multi-phase coil arrangement serves to produce a rotor-deflecting magnetic field as a function of control signals which are applied to coils of the coil arrangement. For this purpose, the coil arrangement has several coils without a stator body of high magnetic conductivity and without magnetic return, the coils surrounding the rotor and being positioned at an equal angular distance apart and being adapted to be controlled by sinusoidal voltages which have a given phase shift relative and each other. The coil arrangement consists, in particular, of two coils which are arranged at right angles to each other and are fed with two sinusoidal voltages which are 90.degree. apart The axis of rotation or rotary shaft can be the seconds shaft or the minutes shaft of the clockwork. In the latter case, a minute hand is fastened on one end of the rotary shaft, which minute hand can be moved over a dial. An hour wheel is driven via a drive pinion arranged on the rotary shaft and a minute wheel, the hour wheel having an hour tube surrounding the rotary shaft An hour hand which can be moved over the dial is fastened on the hour tube. A disadvantage of this motor is that the motor must be fed continuously with sinusoidal voltages resulting in a correspondingly high expenditure of energy. This is true, in particular, when the motor is used to drive a clock in connection with which the space available for arranging a battery is limited.
The prior art also includes an electric tachometer with a pulse motor and a transmission connected thereto which includes a hydraulic damping device (European OS 0 048 459). The damping device comprises a spring by which a worm wheel, which is connected to a motor shaft, is connected to an indicator-hand shaft which extends into an oil dashpot. The motor has coils of a plurality of poles which are fed by an electronic control device with different pulses depending on the direction of rotation of the indicator-hand shaft required to indicate the speed. No details of the motor are disclosed.
To the extent, however, that other known stepping motors which can be fed with pulses have an iron stator which produces a action, one should consider single-phase stepping motors which can only be operated n one direction of rotation and thus do not permit resetting. The manufacture of a ferromagnetic stator with salient poles is expensive. Overshooting of the rotor may under certain circumstances take place upon entrance into the detent positions. Separate damping is required if such a noise-producing entrance is to be avoided.